Snowmelt in Summer

This makes sense is if you can use the snow melt boilers for heating the pool. In that case you already have the HX, so you are only adding in the controls to use the driveway heat when warm. The article @hot_rod linked to has good points on how to set it up and control it.

The one challenge with this setup is you need to protect the HX in the winter time from freezing.

you don’t see or hear of many, maybe the numbers don’t work so well.

The fittings, hx and parts to tie into the 4” piping may be more than what it contributes to the load ?

If you spend the $$ for 6x6 mesh, that goes over the insulation, tube ties to it, lifted an inch

Then rebar lies on top of the tube. That is the best shot of getting everything in a good location in the pour.

#4 bar, 1/3” will be 1” where the bar crosses

Rebar at the bottom doesn’t do much good, just as tube at the bottom is not so good

Given a choice Id rather the rebar in the slab center as opposed to the tube

If the rebar cannot be encased in the slab, might just as well eliminate it.

3/4 tube 6” on center will be tricky. You will need room to make big “light bulb” loop ends

It is the prep work, compaction below that has more to do with a good slab.

What is the true R value and psi rating of that tarp?

Common Dow or Owens foamboard 250 is 25 psi

The 150 board is 15 psi

Personally I feel those nob foam panels are a bad idea. Puts the tube at the worse spot in the pour, at the bottom. It creates air space around and under the tube, and the foam nobs isolate concrete away from the tube.

Tube at the bottom of a slab slows response time, requires higher SWT, and increses downward loss.

Yet another product that has not had a lot of independent testing. IMO.

Here is what the bottom of a slab on nob panels looks like.

It's worth some time getting the tube into the slab, surrounded by a conductor. Like concrete :)

https://www.pmmag.com/articles/101229-john-siegenthaler-tell-me-more-about-nubbed-foam-panels

Insultarp is literally just a thin concrete blanket with a few layers of the thin roll foam you'd see in packing boxes. When compressed under the weight of the concrete, R value goes to almost nothing so it's effectively just a really expensive vapor barrier.

I guess I have to ask you these questions if the driveway is not already completed:

How many square feet is this driveway? are the approach aprons to a garage to be heated?

Have you even considered using continuous overlapping loops of black poly pipe tied to the reinforcing mech every 6 inches to heat the driveway from one end to the other to simplify things with a single return?

This was how my fathers 8 bay car wash floor and approach aprons were heated from October 1st to May 1st every fiscal year in New York State.

Why and how has a 2,400,000 BTU figure been contemplated?

A simple small coal stoker boiler can provide all the hot water you need for snow melt and pool heating with one 110 volt stoker using summer operating temperatures of 140 Degrees Fahrenheit low limit and 160 Degrees Fahrheit high limit hat could be powered with a generator if the power goes out.

The idea is to create a huge thermal mass early and use it to its advantage allowing to be continuously heated at a low rate which in my fathers car wash case was 160 degrees Fahrenheit.

There are car washes that still use coal for fuel to heat their hot water and the car wash floors.

Plenty of info and opinions on the web if you sear4ch a little.

https://www.jlconline.com/how-to/insulation/are-bubble-wrap-r-value-claims-accurate_o/

I believe this is the compliance work around.

I suppose you could run some numbers and come up with a dollar amount difference running that system for the next 20 years or so with R-1 vs R-7.5 or 10.

Ramp up time to melt will be shortened with a good insulation package, also.

Or maybe the owners are not so energy conscious?

Save your client some money and suggest they use black PVC in tight loops with 6 inch separations from beginning to end with a single return back to the boiler. Adding a 1,000 gallon solar storage tank with 5-6 coils in it will only save them more money. Universities use poly pipe and hot water in walking paths to keep them ice free.

Edited today;

I have neglected to add that the black poly pipe is also an oxygen barrier pipe and much less expensive than pex.

High Density Polyethylene pipe (HDPE) would be fine for a snow melt application and much less expensive. Laying the HDPE pipe in four inch loops would work well.

Using the car wash example in my fathers case the black poly pipe over lapped and each loop separated by a six in spacing and it allowed may many more feet of tubing to heat the car wash approach aprons and the main slab surrounding the car wash pit.

Overlapping the tubing in four or six inch loop increments allows the black poly tubing to heat every square inch more effectively with one circulator because the concrete slab is absorbing the heat from the tubing.

The HDPE could be tied to the reinforcing mesh with black cable ties to secure it.

With a car wash and for that matter any heated slab keeping the slab warm continuously allows the system to maintain a balanced temperature for the entire heating season with a lower temperature heating fluid like non-toxic antifreeze or standard automotive antifreeze.

A 8,000 pound wet(neat) sand mix concrete would work well and not erode as quickly compared to a gravel mix concrete and the sand mix would more easily be vibrated into place eliminating air bubbles.

Buying the HDPE pipe in a large reel will save them a great deal of money.

You could purchase a large enough reel of 3/4 HDPE pipe which is oxygen barrier pipe anyway to do the entire driveway looping the HDPE pipe in 4 inch loops from beginning to end with one return to the boiler. Using 3/4" HDPE pipe in loops may consume more pipe for this installation but that would only benefit the home owner with a larger thermal mass in all seasons using continuous loops from the parking circle to the bottom of the driveway and back to the boiler in one loop.

Using water in the example 40,000" linear feet of HDPE 3/4" pipe would carry 1,207 gallons of water in the example.

snowmelt systems typically have gave glycol, so you want to use a tubing with an oxygen barrier

O2 will migrate through the wall of typical HDPE and breakdown the glycol turning it acidic